Logical Operators
Common logical operators include AND, OR, and NOT. The operation result can be TRUE, FALSE, or NULL (which means unknown). The priorities of the operators are as follows: NOT > AND > OR.
Table 1 lists the calculation rules, where A and B represent logical expressions.
| Operator | Result Type | Description |
|---|---|---|
| A AND B | BOOLEAN | If A and B are TRUE, then TRUE is returned. Otherwise, FALSE is returned. If A or B is NULL, then NULL is returned. |
| A OR B | BOOLEAN | If A or B is TRUE, then TRUE is returned. Otherwise, FALSE is returned. If A or B is NULL, then NULL is returned. If one is TRUE and the other is NULL, then TRUE is returned. |
| NOT A | BOOLEAN | If A is FALSE, then TRUE is returned. If A is NULL, then NULL is returned. Otherwise, FALSE is returned. |
| ! A | BOOLEAN | Same as NOT A. |
| A IN (val1, val2, ...) | BOOLEAN | If A is equal to any value in (val1, val2, ...), then TRUE is returned. Otherwise, FALSE is returned. |
| A NOT IN (val1, val2, ...) | BOOLEAN | If A is not equal to any value in (val1, val2, ...), then TRUE is returned. Otherwise, FALSE is returned. |
| EXISTS (subquery) | BOOLEAN | If the result of any subquery contains at least one line, then TRUE is returned. Otherwise, FALSE is returned. |
| NOT EXISTS (subquery) | BOOLEAN | If the subquery output does not contain any row, TRUE is returned; otherwise, FALSE is returned. |
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